This invention relates to a process for the biological purification of wastewater wherein the wastewater is treated in a purification plant comprising at least one storage tank and at least one biological treatment stage, as well as to an apparatus for conducting the process.
In the biological purification of wastewater, a storage tank is conventionally connected upstream of a biological treatment stage, the latter usually comprising a trickling filter or an aeration tank. By passing entering wastewater first to the storage tank and then to the biological treatment stage, it is usually possible to compensate for the fact that the wastewater is not constant relative to flow rate and/or composition. To achieve the desired relatively constant values regarding quantity and concentration of waste in the effluent leaving the storage tank, the storage tank must be very large on the one hand and optimally should be equipped with blending means for the wastewater, for example, with agitators. There are limits, however, to the provision of such storage tanks or lagoons in many cases, due to the fact that the acreage required is either unavailable or the cost of the land is prohibitive. Furthermore, the use of agitation or the like for the storage tanks results in not only increased investment costs, but also substantially increased operating and maintenance costs.